The light fingered String Quartet
Finally, we come to look at the action of fingering and making the notes at the right pitch and at the right time that end up being the music. Many people think this is the most important and difficult part of violin playing, and indeed some teachers teach if this were the case, very much ignoring the effect of the bowing of the instrument. But it is a fundamental part of playing the violin and the part that if it is wrong is immediately and painfully, or sometimes hilariously, obvious.
As I said earlier, the note pitch is achieved by stopping a string with a finger to alter the length of string that can vibrate between finger and instrument bridge.
The position of the fingers is of course critical. With a guitar there are frets, metal strips across the fingerboard against which the musicians finger presses the string. The length of string that vibrates to create the note pitch is the distance between the metal strip and the bridge of the guitar. It is not too critical where the finger is placed. So long as it is somewhere between the two frets, that is good enough. ( this is not quite through for more chance players, put as rule of thumb it's good enough.)
With a violin there are no frets across the fingerboard, No marks, no indentation. The fingerboard is completely smooth. (This isn't the case with a baroque Viol which has threats made of strips of got tied in place.) This has to be the case so that one can achieve slides between notes, as particularly prevalent in Irish ceilidh music, slide into position on high notes, as is both the style and necessity in playing romantic sting quartets or violin concertos, or doing ornamentations that are typical of the Scottish ceilidh idiom.
So the note that is played is a function entirely of the distance of a string between the finger and the violin bridge. Not only that, but the finger is a soft squishy object with a bone inside it. It is not even a precise object to stop the stream. It is not even like a Hawaiian guitar, where the musician puts a metal tube on their finger so that they can slide it up and down the strings or hold it in a particular position to play a note. This turns the finger from an imprecise squidgy object into a physically accurate object, a metal tube.
Add to this that the distance between one note and the next, perhaps the note played with the first finger or index finger and the next note played with the second finger, not only varies depending on whether the musician is wanting a tone or a semitone between the notes, but varies with the position along the fingerboard. As the player moves higher up to fingerboard, from 1st to 2nd to 3rd position excetera, the distance between fingers to play a tone, reduces. In very high positioned close to the bridge, the fingers can be too fat to play an interval of a tone, and one finger has to be moved out of the way before the next thing you can be put down.
Add to this that in first position ie near the neck of the violin, a movement of the Finger of about half a millimetre can be the difference between being in tune and out of tune, and high up the instruments the accuracy may have to be better than a tenth of a millimetre to achieve the right note without detecting an error in intonation. This accuracy is impossible to achieve by the feel of where the musician is putting their finger. Violinist can guess where to put their finger from past experience, but can only ever put it approximately in the right place.
The body has sensors in muscles and joint areas of the body, the wrist the hand the fingers and so on, that can tell the brain where the particular body part is. If you look at a glass sitting on the table in front of you, with care you can shut your eyes and pick up the glass. The accuracy of these position sensors is sufficient to take you too close to the glass without knocking it over, but it is not accurate enough to enable you to pick up the glass without spilling it's contents without some additional information. When picking up a glass with your eyes closed, that additional information comes from the touch sensors at the end of your fingertips. They are very sensitive to pressure. This touching and pressure information is fed back to the brain and gives information about errors in your hand position relative to the glass, and without you thinking about it or being consciously aware of it, whose touch sensors combined with the position sensors within the arms and hand enabling you to pick up the glass without looking at it.
So playing a violin in tune, and hitting the right notes is rather like picking up a glass blindfolded, but there is an additional feedback loop. Blindfolding is relevant. A violinist does not look at their fingers as they play. A learner will always try and look at their fingers and I suppose this is a part of the initial learning process, seeing where their fingers are being placed and on which string. Just soon as possible though, they have to be persuaded not to look at their fingers as sight doesn't play a part in achieving the intonation of a violin. The action of sight that is normally used to help pick up a glass safely, is replaced by the action of the ears.
There are 3 feedback Loops to the brain that are active in playing a violin to the right pitch. The first feedback loop is from the position sensors in arm, hand and fingers which tell the brain roughly where the finger is. The second feedback loop uses touch sensor information from the Fingertips, the sides of the fingers and thumb that touch the neck of a violin and possibly, at higher positions on the instrument, touch sensors from the heel and palm of the hand as they touch the soundbox of the instrument. The third feedback loop uses information from the ears about the frequency of the note that is being played, and this is the most important feedback loop for accurate intonation.
Whereas the first feedback loops give approximate positions of the fingers, it is the final auditory feedback loop that allows the finger to be positioned to a fraction of a millimetre accuracy and correct errors in finger position within a fraction of a second.
Closed loop feedback systems must have a reference against which to work. The whole point of a closed loop feedback system is that, whatever kind of system it is, it is measuring the error between some ideal reference and actuality. Closed loop feedback systems don't just relate to positional systems as with a violinist's fingers, but to the control fins on a guided missile, or the cutting head of a CNC machine Tool. Closed loop can equally well work with temperature control in a chemical works for your central heating system (if you've got a high class heating system with proper control.)
So the question is, what is the reference for this feedback system on a violin? The answer is your imagination. To be able to play a violin in tune you have to know in your own mind what the sound should be like. You have to hear the tune correctly in your head so that the feedback system, including information from your ears, can be used by your brain to find the area between the note imagining and the note playing.
When you describe it as I have done, it all sounds very complicated. This process is going on for each note played. There may be several notes per second and for each one this process has to be gone through. Obviously, if you were having to think about it and do it consciously, you would never be able to do it. You would only be able to play one note every few seconds. Of course this is precisely what happens when you are learning the violin, or any instrument for that matter. You start off by playing each note very slowly and very purposefully. You think about what you are doing wrong and you work out how to make corrections. Only by doing this time and time again in a process called practice, can this process become automatic.
What is happening is that you are teaching the automatic or subconscious part of your brain to do all the things that I've described above. You don't teach it by discussing it intellectually like I have done in my text above, you teach it by example. Running through the process very slowly and deliberately, the neural networks of your subconscious mind adjust themselves and build up connections which produce the actions that you are training it to do. You are training your neural networks.
Neural networks can be created in electronic hardware or in software on digital computers and these are trained in a similar way. They may be trained by the engineer who gives the computer examples of whatever it is that the network is being trained for. For example, if it is a neural network to identify the difference between photographs of men and women, the trainer would show multiple examples of men and women, telling the computer which is Which. After a while the neural network begins to identify a proportion of the pictures correctly. The trainer's job is then to correct the errors and as it does so the neural network, if it is properly constructed, will get better and better at identify which of the pictures of male and which are female. Neural networks can achieve equal or better results than a human for a great many of tasks.
So with violin practice, a musician is learning how to do the playing automatically. They are training the neural networks of their subconscious to take information from all these feedback Loops simultaneously, to compare it with the notes they are anticipating as they think of the Note or hum the tune in the head, or the player may pitch the note in their head from the musical notation that they are reading. Pitching the note in this way from musical score allows somebody to play a piece of music they have never heard before, correctly the first time they try. They may not be consciously aware that this is what they are doing, but in effect it is the process that the automatic part of their mind is going through. This is why it can be so difficult for somebody who has learnt to play from music, where the pithing that happens in their imagination comes from the dots they are reading on the manuscript paper, to play by ear, where the imagination that links the sound to the notes being played is coming from another part of their memory.